(i) Omega-3 Essential Fatty Acids
Health experts have concluded that a large percentage of the population have a diet which is deficient in long chain, highly unsaturated essential fatty acids. For example, it is estimated that 80% of all Americans have a deficiency. As many as 60 medical conditions are linked to this deficiency or have been identified as benefiting from Omega-3 supplementation.
The three most important of the long chain fatty acids are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic (DPA). These fatty acids are deemed “essential” because they have a vital role in maintaining the integrity and fluidity of the membrane which surrounds human cells and because they cannot be synthesized by the body. Without a healthy membrane, the ability of cells to hold water, nutrients and electrolytes is impaired. As a consequence, the membrane may no longer protect the cell from damage caused by free radicals which are the products of oxidation within the body. They also lose their receptivity to hormones and their ability to relay chemically encoded instructions for cellular repair.
The search by health conscious consumers for foods containing omega-3 fatty acids can be a frustrating one. Given the trend toward mass production and packaging of meals and meal ingredients, consumers have less knowledge of, or influence over the contents of their food. The move by some manufacturers toward mono or polyunsaturated fats as substitutes for saturated fats is a positive step. Generally however, the polyunsaturates most often selected are those derived from vegetable oils which contain significant amounts of omega 6 but little or no omega-3. While omega 6 and omega-3 fatty acids are both necessary to good health, most health experts agree that, they should be consumed in a balance of 4:1 respectively. Today's Western diet has created a serious imbalance with current consumption on average of 20 times more omega 6 than omega-3. Concerned consumers have begun to look for health food supplements to restore the equilibrium. Three major sources of omega-3 supplements are flaxseed oil, fish oils, and seal oil.
The past decade has seen rapid growth in the production of flaxseed and fish oils. Both types of oil are considered to be good dietary sources of polyunsaturated fats but are less effective than seal oil in supplying omega-3 fatty acids. Flaxseed oil contains no EPA, DHA or DPA but rather contains alpha-linolenic acid—a precursor to EPA. There is evidence however that the rate of metabolic conversion can be slow and unreliable. Some research has shown that supplementation with flaxseed oil may result in higher tissue levels of alpha-linolenic acid without any corresponding increase in EPA.
Fish oils vary considerably in the type and level of fatty acid composition depending on the particular species and their diets. For example, fish raised by aquaculture tend to have a lower level of omega-3 fatty acids than those in the wild. some research has shown that seal oil is more beneficial to those at risk of heart disease and diabetes than is fish oil. The relative absence of DPA in fish oil and the slower rate at which the body assimilates EPA and DHA from fish oils have been cited as factors.
The most direct and complete source of omega-3 oils is found in the blubber of certain marine mammals, especially the harp seal. Among its advantages is that the body's absorption of omega-3 from seal blubber is faster and more thorough than is the case with flaxseed and fish oils. This is due, in part, to the molecular configurations of the EPA and DHA in seal oil which varies slightly from that found in fish oils. The essential fatty acids found in seal oil include a high level of DPA (up to ten times that of fish oils). There is growing evidence that DPA is the most important of the essential fatty acids in keeping artery walls soft and plaque free. A further advantage of seal oil is that it is more stable than fish oil and less vulnerable to the natural process of oxidation. However, there are challenges in producing a satisfactory grade seal oil for administration as a dietary supplement to humans. Seal oils, like other health food oils, are susceptible the natural process of oxidation. The primary and secondary products of oxidation may give rise to unacceptable flavours and odours in the oil, impair digestibility of the oil, and produce fee radicals which can damage or destroy the body's cells.
The causes of oxidation include exposure to air, heat, light (“harmful light” refers to light in the range of about 4,250–5,100 angstrom), oxygen and certain metals such as iron. Oxidation of polyunsaturated oils limit their shelf life. As fish and seal oils become oxidized their taste and odour may become objectionalble. For example, one study of encapsulated fish and plant oil samples found that many commercially prepared oils had poor oxidative stability (VKS Shuklia, EG Perkins, “Rancidity in encapsulated health-food oils”, Inform, vol. 9, no. 10 (October 1998)). Clearly there is a need for nutritional oils that offer higher levels of oxidative stability.
Health Canada recommends that the daily diet contain at least 1.8 grams of omega-3 fatty acids. The U.S. Department of Health and Nutrition Services has also acknowledged that health benefits would accrue to the general population if dietary intakes of omega-3 polyunsaturated fatty acids (PUFA) were increased. At present, the average consumption of omega-3 PUFA in North America and Europe is less than one gram per day. The administration of seal oil as a dietary supplement could fill this gap if a suitable refined oil could be produced.
(ii) Oil Refining
In the processing of food oils and fats from animal, vegetable and marine sources, it is important to produce edible oil and fat products that have a bland, neutral taste for several months after processing. To obtain an oil with these characteristics, it is essential to remove compounds that give flavor to the oil as well as compounds that are detrimental to oxidative stability. It is also desirable to significantly reduce, if not eliminate, chemical contaminants such as PCBs and pesticides.
The concentrations of objectionable compounds vary in the different oils, depending on the source. Many of the common vegetable oils contain phosphatides, colored compounds and their breakdown products, oxidation products of triglycerides, dissolved and suspended proteinaceous material, free fatty acids, pesticides, pro-oxidant metals and pesticides.
Oils derived from marine sources, mammalian and fish, are very low in phosphatides and may be low in colored compounds, but proteinaceous and mucilagenous materials, breakdown products from triglyceride oxidation, and concentrations of calcium and magnesium and pro-oxidant metals are more significant, as well as pesticides. Most importantly, these oils are more sensitive to oxidative deterioration because of the highly unsaturated fatty acids present. They also contain only insignificant amounts of natural antioxidants, such as the tocopherols that are present in significant amounts in most vegetable oils.
The oils of marine origin also have a very intense fishy odor and taste, which originates with protein, mucilage and triglyceride breakdown products. The odor and taste compounds and their precursors must be removed to extremely low levels to make the oil more suitable for food uses and to improve their flavor stability after processing.
Experience in processing the oils from the above sources has shown that to achieve sufficiently complete removal of objectionable substances requires several ‘refining’ steps. These refining steps are described for the various oils in Bailey's Industrial Oil & Fat Products, Fifth Edition, Volume 2. The refining steps comprise the following:                Degumming—alkali refining—bleaching—deodorizing.        
The degumming process serves to remove phosphatides and other mucilagenous compounds from the oil and is especially important with vegetable oils. Water alone, water and acids such as phosphoric acid, or water and other chemicals are used. Using water alone does not remove phosphatides to the required low concentration.
The alkali refining process serves to remove free fatty acids and phosphatides, especially the non-hydratable phosphatides, mucilagenous and proteinaceous material to very low concentrations. Some of the coloured compounds and the trace metals that occur in oils are also removed. Sodium hydroxide solution is commonly used, sometimes after a pretreatment with an acid such as phosphoric acid. Serious disadvantages of the process are that oil losses tend to be high (because of entrainment of oil in the soap phase), and there is a need to remove fat and chemicals from the water in the process to make it acceptable for discharge. U.S. Pat. No. 5,855,944 (Kochinski, 1999) and U.S. Pat. No. 5,264,597 (Van Dalen et al., 1993) are two examples of prior art patents that use alkali refining.
The alkali refined oil is water-washed to remove small amounts of soap and phosphatides. Water washing is sometimes replaced by treating the oil with small amounts of silica gel, which serves to remove residual amounts of phosphatides and soaps before bleaching. This saves some of the water treatment costs associated with alkali refining.
Bleaching with activated bleaching earth is used to remove colored compounds, especially chlorophylloid and carotenoid material, but also small amounts of phosphatides and soap still left in the oil after alkali refining.
Deodorization primarily removes flavor and odor compounds and small amounts of free fatty acids by distillation. The process is carried out at very low pressures and relatively high temperatures (about 260° C.) using steam as a carrier gas to strip the volatile flavor and odor compounds and free fatty acids from the oil. The success of this step depends on the oil having been thoroughly ‘refined’ in the processing steps outlined above, except for removal of free fatty acids. Because of the relatively high temperatures that must be used in deodorizing, inadequate removal of flavor and color precursors easily lead to new formation of such compounds and hence oils of poor flavor and flavor stability and high color.
The above sequence of processing, or ‘refining’ steps is sometimes modified. For example, degumming and alkali refining can be combined in a single operation followed by bleaching and deodorizing.
Further, alkali refining can be omitted in some cases in favor of degumming alone with chemicals and water. This is then followed by an acid treatment of the oil before adding bleaching clay and bleaching the oil, and then deodorizing. Alternatively, chemically degummed oil may be treated with silica gel to reduce phosphatides still further, as is described, for example in U.S. Pat. No. 5,069,829 to Van Dalen et al, and in U.S. Pat. No. 4,880,574 to Welsh.
When alkali refining is not used, the deodorizing step is relied upon to remove the free fatty acids from the original, relatively high concentration in the oil to the required low concentration, as mentioned earlier. There are, thus, no fatty acid soaps to be processed and waste water to be treated, as in alkali refining, and the process losses are lower. The deodorizing conditions, however must be somewhat more extreme than are applied with alkali refined oils (temperature, time, steam usage). It is important to note that with vegetable oils and animal fats, which do not contain highly unsaturated fatty acids, the danger of isomerization when somewhat extreme deodorizing temperatures and times are used is not a factor, but with unhydrogenated oils of marine origin this has not been done.
Oils of marine origin are invariably alkali refined and may receive an acid pretreatment before alkali refining to precipitate calcium, magnesium and other trace elements, which are then removed in the alkali refining step. The processing of oils of marine origin is described in Seal Fishery and Product Development, F. Shahidi, p. 109–111, Science Tech Publishing Company, St. John's NF, 1998. Chang in U.S. Pat. No. 4,874,629 and Takao in U.S. Pat. No. 4,623,488 refer to this along with bleaching as part of the processing steps required to produce fish oils for food use.
Because of their high unsaturation and ease of oxidation and, hence, their great sensitivity with respect to achieving a bland, flavor stable product for use in edible oil products, it is very important to achieve essentially total removal of the deleterious components in the crude oil. This is required even when these oils are hydrogenated to make them more saturated and stable towards oxidation before use as a food. The danger of inadequate removal, especially of soluble proteinaceous materials and of pro-oxidant metals, primarily iron, and of other deleterious compounds when alkali refining is not applied, is considered too great.
As discussed above, there is now emphasis on using oils of marine origin, unhydrogenated, for their special nutritional qualities due to their content of highly unsaturated, long-chain fatty acids (eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid, usually described as EPA, DPA and DHA, or as omega-3 fatty acids) in their triglycerides. Hydrogenation to achieve better stability would destroy the special nutritional qualities of these fatty acids. With the unhydrogenated oils, the thorough removal of oil components deleterious to achieving a bland, flavor-stable oil is then even more important than with other oils.
At the same time, it is also advantageous with these highly sensitive oils to reduce the refining steps and eliminate the use of chemicals as much as possible. This minimizes the chances for exposure to air, and the need for repeated heating of the oils, or for extended periods of time, and the chance for the formation of chemical artifacts with the highly unsaturated fatty acids present. If achieved, it would then be possible to provide an oil for nutraceutical and other food uses that has excellent organoleptic properties without any decrease in the concentration of the nutritionally important EPA, DPA and DHA, and with a minimum of breakdown products, free fatty acids, colored compounds, pro-oxidant metals, pesticide residues and chemical artifacts.